1. Field of the Invention
This invention relates generally to surgical access devices and more specifically to valves and seals associated with such devices.
2. Discussion of the Related Art
Access devices are commonly used to facilitate the introduction of surgical instruments into body conduits and body cavities. One such device, which is typically referred to as a trocar, is used in laparoscopic procedures to provide access through the abdominal wall and into the abdominal cavity. In laparoscopic surgeries, the abdominal cavity is commonly inflated or insufflated in order to increase the volume of the working environment. Under these circumstances, valves are provided in a valve housing of the trocar to inhibit the escape of the insufflation gas. The valves form an instrument seal in the presence of an instrument, and a zero seal in the absence of an instrument.
Trocar seals are disclosed and claimed in applicant's U.S. Pat. No. 5,385,553, which is incorporated herein by reference. This patent discusses the problems which can be encountered when the instrument is inserted off-axis. The solution of floating the valve is discussed in detail.
In this patent it is contemplated that the valve would comprise first portions which define an orifice through the valve and second portions disposed outwardly of the first portions. These second portions are intended to provide a greater flexibility than the first portions. As a consequence, when an instrument is inserted off-axis, the second portions will deform while the first portions, which form the instrument seal, will remain undeformed. One of the embodiments contemplates provision of an excess of material disposed outwardly of the valve orifice which functions generally as a bellows. In this case the first portions of the valve have a first radial length to radial distance ratio while the second portions of the valve have a second radial length to radial distance ratio. The valving mechanism is formed generally of a solid but elastomeric material.